For a projection-type display device (projector) that includes a lamp unit, cooling is essential to secure performance and reliability. To cool an object to be cooled such as a light source lamp that is a heating element, conventionally, in the projection-type display device, there has widely been used a method for discharging heat from the device by a cooling fan or supplying a cooling wind to the object to be cooled.
For example, Patent Document 1 discusses a projector that includes, in addition to a cooling fan, a cooling device configured to cool a heating element by blowing air compressed by a pump to the heating element. The light-source lamp cooling device discussed in Patent Document 1 includes a pump that compresses air, an injection unit that injects the compressed air, and a pipe that connects a gap compressor to the injection unit. In the device discussed in Patent Document 1, to prevent reduction in the amount of air that is injected caused by clogging of injection holes of the injection unit with dust, which in turn sets the light source lamp in an overheated state, control is performed to detect pressure in the pipe and turn the light source lamp off when the pressure in the pipe reaches a predetermined value or more.
Patent Document 2 discusses a projector that includes an air pump. The projector discussed in Patent Document 1 includes an air discharge unit that injects compressed air to a light source, and a tube that is a storage unit to store the compressed air. In the device discussed in Patent Document 2, control is performed in such a manner that the amount of air in the tube is increased by the air pump to increase the flow rate of air discharged from the air discharge unit when pressure in the tube is lower than a target value, and such that the amount of air in the tube is decreased by the air pump to reduce the flow rate of air discharged from the air discharge unit when the pressure in the tube is higher that the target value. This control enables prevention of overheating of the light source by keeping the flow rate of air constant for the light source.
Thus, conventionally, in the projector that includes the pump configured to inject the compressed air, highly accurate control is performed for the pump. In cooling by the pump, a certain level of cooling performance is acquired by utilizing a gauge manometer not affected by atmospheric pressure.
In the case of the abovementioned cooling method that uses air as a cooling medium, cooling performance of the pump and the cooling fan are affected by atmospheric pressure. In other words, when the projector is used in an environment of a high altitude, the air density becomes low due to low atmospheric pressure, and hence the object to be cooled may not be sufficiently cooled even when cooling control similar to that at a low altitude is performed. The current projector therefore has a cooling mode exclusive to a high altitude. When the projector is used at a high altitude, a user himself switches a cooling mode to that for the high altitude. However, in the method having its cooling control dependent on the user, it is difficult to completely implement cooling that takes a difference in altitude into consideration.
Thus, atmospheric pressure must be detected, and cooling control corresponding to the air density at this atmospheric pressure must be performed. Patent Document 3 discuses a projection-type display device that employs a method for directly measuring atmospheric pressure by using an absolute manometer such as Torricelli tube barometer or an aneroid barometer.    [Patent Document 1] JP2008-90062A    [Patent Document 2] JP2008-90161A    [Patent Document 3] JP2000-194072A